Okayama Mabicho, a newly-built house in western Japan suffering heavy rains.

According to NHK's report, 30% of the newly built houses are single-story houses in Mabi-cho, Kurashiki City, Okayama Prefecture, where many people were killed due to flooding to the second floor and above due to heavy rain in western Japan. I understand. Experts pointed out that early evacuation is important, and pointed out that "even if we should escape late, we need to prepare many buildings on the second floor and above that can be evacuated in the area."

Heavy rains in western Japan flooded a wide area in Mabi-cho, Kurashiki city, causing widespread flooding, killing 51 people excluding disaster-related deaths, of which 80% (41 people) were single-story homes or two-story houses. Found on the first floor of.

In many buildings, flooding reached the height of the second floor, making it difficult to even "vertical evacuation" to evacuate to the second floor and above.

Under such circumstances, when NHK investigated the houses built after the heavy rain based on the “building plan summary” submitted to the city, 32% of the 953 buildings constructed by the end of March this year. It turned out that 307 buildings, which corresponded to it, were single-storey.

Last year, it was three times the ratio of one-story houses to new houses built nationwide.

Regarding the reason for building a one-storied house, the residents said that "we could not build a house with more than two stories due to lack of funds" or "it is difficult to go up to the second floor because we are old and have bad legs."

Measures such as strengthening the function of the embankment are being carried out in Mabi-machi, Kurashiki City, but it will take until the end of 2023, and according to the Ministry of Land, Infrastructure, Transport and Tourism, the risk of inundation will not be zero even after the construction is completed. is.

Professor Takaaki Kato of the Institute of Industrial Science, University of Tokyo, who is familiar with disaster-resistant town development, said that it is important to move to a safe place early if heavy rain is expected. With that in mind, it is necessary to prepare a large number of buildings on the second floor and above that can be evacuated if there is a delay in escape," he said.

Rebuilding a house in a one-story house

One of the areas where the ratio of newly built houses to flat houses in Mabi-cho, Kurashiki City is particularly high is the Tanaka housing complex in the Yasuda area.

Due to the heavy rain in western Japan, most of the houses were flooded to the second floor, and all 34 households were completely destroyed.

When I checked based on the "Building Plan Summary", 15 new houses were built in this area by the end of March.

Of these, 9 were 60% flat.

According to the self-government chairman of this estate, there was no single-story house in this area at the time of heavy rain, and most new builders were only elderly households.

The couple, Mr. Hiroo Furusawa (73) and Mr. Setsuko (72), who live in this housing complex, also built a new one-story house.

A two-story home built about 40 years ago was completely destroyed by the heavy rain in western Japan.

Immediately after that, he moved into a temporary housing unit in Kurashiki City, about 7 km away, but he didn't know anyone near him, and he said that he started to feel stressed from living in an unfamiliar place.

When I returned to Mabi-cho, I was still worried that I would be flooded again, so I thought about rebuilding my home in a place other than Mabi-cho where there is no risk of flooding. I thought that I couldn't live comfortably if there weren't many, so I decided to go back to where I was.

I also thought about building a two-story house that can be “vertically evacuated” when there is a risk of flood damage, but it is difficult to cover the reconstruction fund with just the money I have, so when I consulted with a relative working at the bank It is difficult to get a mortgage if you are a pensioner.”

My wife, Setsuko, had fallen injured on the stairs at home where she lived before heavy rain. The decision to build a one-story house was made in consideration of the fact that it will be difficult.

Setsuko said, “I think I would have built a two-story house if I was about 30 years old, but I could not choose the path either in terms of money or physically. I cannot do “vertical evacuation”, so I will not be able to protect against flood damage. Fear doesn't go away, but when the danger of a disaster is imminent, we have no choice but to evacuate to a safe place as soon as possible.

Expert "Securing a large number of shelters"

Professor Takaaki Kato of the Institute of Industrial Science, the University of Tokyo, who is a member of the reconstruction planning promotion committee of Mabi-cho established by Kurashiki City, who is familiar with disaster-resilient town planning, said, "I understand the risks properly and want to escape when there is an emergency. If there is, there is no problem, but it is an impression that 30% of newly built houses are flat houses while the risk of inundation is not zero,'' he said, ``There are many elderly people living in flat houses. As a premise, it is necessary to prepare a large number of buildings on the second floor and above that can escape when heavy rain is expected in the area."

As a concrete example, Professor Kato cites an apartment house that functions as an evacuation center, which was constructed mainly by a welfare office in Mabi-cho, Kurashiki City after a heavy rain in western Japan.

It is a renovation of a two-story apartment, and one room on the second floor is usually used as a communication space for local people, but at the time of a disaster, not only the people living in this apartment but also the one-story surrounding area will live. It is used as a place for the "vertical evacuation" of elderly people.

There is also a slope that connects with the outside of the building, so that people in wheelchairs can smoothly go up to the second floor.

Prof. Kato said, "Similarly in areas where the sea level is above sea level in Tokyo, but if there are many people who choose a flat house, it is necessary to proceed with urban development that can cope with flooding. It is required to coexist with risk by ensuring that the next generation has the same high awareness of disaster prevention."

River repair work in a country or prefecture

For the Oda River and its tributaries that flow through Mabi-cho, Kurashiki City, where the embankment broke due to the heavy rainfall in western Japan, the national government and prefectures are working to expand the width of the embankment and strengthen its functions.

In addition, in order to smooth the flow of water and lower the water level in the Oda River, construction is being carried out to move the confluence of the main stream Takahashi River to the downstream.

With regard to such construction, the government and prefectures aim to complete it by the end of 2023, that is, four years later, according to the Ministry of Land, Infrastructure, Transport and Tourism, and if this is over, it will be flooded even if it rains to the same extent as heavy rain in western Japan. Is that it can be prevented.

After that, the country plans to carry out flood control work such as excavating the riverbed of the Oda River over 20 to 30 years.

However, even if it is completed, it is not possible to withstand the heavy rain of "once every 1000 years", which is obliged to assume in the hazard map, and it has been observed recently such as typhoon 19 last year. This means that even with the "every 100th" class of rain, the risk of inundation does not go to zero.

Gosuke Inoue, Research and Design Manager, Okayama River Office of the Ministry of Land, Infrastructure, Transport and Tourism said, “Mabi town, which is surrounded by two first-class rivers and has a confluence, is topographically dangerous for flooding, and no matter how much river maintenance is done "It is difficult to reduce the risk to zero," he said, "I recognize that some people have no choice but to build a one-story house in the disaster-stricken area. I think we must explain the risks properly in order to promote preparation. I am talking."